August Microphoto of the Month

Written by: Jim Beard

Tuesday August 26, 2014

About 200 million years ago, one of the largest volcanic eruptions in the history of the Earth covered parts of what are now Eurasia, Africa, and North and South America with lava. This volcanic event, termed the Central Atlantic Magmatic Province, is thought to be the cause of a major extinction event at the end of the Triassic period. Many large tabular injections of magma (diabase dikes) that fed the volcanoes are seen even today throughout the Piedmont of Virginia and up and down the east coast. The photo this month is a polarized light (false color) image of a thin section made from a sample of a diabase dike. The colored flecks are the mineral augite. The black and white striped mineral is plagioclase. The field of view is approximately 3 millimeters.